Centrifugal screen separation apparatus



Dec. 20, 1960 2. VANE CENTRIFUGAL SCREEN SEPARATIONAPPARATUS 2Sheets-Sheet 1 Filed May 4, 1959 Iii-ni Dec. 20, 1960 z, v

CENTRIFUGAL SCREEN SEPARATION APPARATUS 2 Sheets-Sheet 2 Filed May 4,1959 United States Patent CENTRIFUGAL SCREEN SEPARATION APPARATUS ZdenekVane, Box 225, P.O. Stn. D, Ottawa, Ontario, Canada Filed May 4, 1959,Ser. No. 810,687

1 Claim. (Cl. 209-211) This invention relates to improvements inseparating methods and apparatus, and more particularly to multipleseparations of suspended solid particles by density difference.

In the prior art, the starting point for density separations of finesolids is a completely stratified mixture in a spinning carrier.Generally, the components are separated from the stratified mixture in aradial or axial direction. When the product of the separation is to betreated again, as it is necessary for instance to separate an excess ofthe carrier from the solid component, such secondary separation is to beperformed in a new apparatus, or apparatus section. Consequently,conventional apparatus possess little compactness of structure anduniformity of method, and are often a mere aggregation of separators,wherein intermediate steps of evacuating and refeeding, conveying andpropelling the handled materials accompany a positive separation work.In this invention, spinning particles in suspension are separated outinto concentric layers of different density ranges through the action ofa free vortex of carrier fluid spinning helically, and are interceptedduring their radially outward travel by a system of concentric sleeves.The spin and the radial spreading is continued within said system, thefirst separation being followed by one or several subsequentseparations, using the same primary spin. In this novel method, thestarting point of separation is the discharging of a concentratedseparable material into a spinning column of a pure carrier fluid. Asthe stratification of the separable mixture proceeds, the resultingdensity layers are intercepted by separating means. This novel methoddivides the spinning carrier into layers wherein the separable materialjust started to be stratified according to density, and is, therefore,able to operate more economically by treating one separable component intwo or more separation steps performed in the same separation chamberwhile spinning the separable material only once. Moreover, the separablematter spreading in a radially outward direction, being compelledthrough the carrier fluid spinning radially inward and subjected to aminute pressure control, allows for a high precision of density ofseparated components. In this invention, the separation of the particlesand the evacuation of the carrier fluid are performed in a compactstructure, thereby saving in construction material, power of operation,time of separation, and in wear by abrasion.

It is an object of this invention to provide a novel method andapparatus for multiple separations of suspended particles according todensity by spreading fine solids in a spinning carrier from the centerthereof and by intercepting the carrier with therein suspended solidparticles during its flow in an axial direction by a system ofseparating sleeve partitions.

Another object of the invention is to provide a novel compact structurefor further sub-separating the product of the primary separation.

Still another object of the invention is to provide a method andstructure for density separations of suspended very short sleeve 29. Anannular space 31' Patented Dec. 20, 1960 Other objects of this inventionwill become apparentv from the following description and accompanyingdrawings in which Figure 1 is a longitudinal section of my newapparatus,

Figure 2 shows a horizontal section of thesame along the line 2-2 inFigure 1,

Figure 3 represents a modification of my new apparatus in section,

Figure 4 shows, somewhat schematically, a proposed volume control forthe same apparatus, and

Figure 5 is a modification of an embodiment of the apparatus in Figure1.

Figure 1 shows the novel apparatus wherein the numeral 11 generallydesignates a shell defining a vortex chamber. The upper part of theseparator is provided with a tight cover 12, the lower part with aconically shaped bottom 13. The cover 12 supports a flange 14, wherein afeeding pipe 15 can slide in an axial direction, said movement beingcontrolled by any suitable conventional means, as for example a toothedgear 16, fastened in a bracket 17. A stufling box 18 secures a tightconnection of the two parts, 12 and 15. Adjacent to its discharge nozzle19, the feeding pipe 15 is provided with spin imparting vanes 20, of theconventional type known. The concentrated separable material isdischarged at the nozzle 19. The carrier fluid is entered by the feedingpipe 21, through the tangential inlet 22, into the vortex chamber 23. Inthe bottom 13, a series of intercepting partition sleeves 24, 25 and 26are provided concentrically below the discharge nozzle 19. The sleeve 24is placed centrally in the vertical path of said nozzle 19; the sleeves25 and 26 are placed concentrically, in a downwardly sloping sequencearound the sleeve 24, forming the annular spaces 25' and 26, and thatone marked by numeral 31, between the sleeve 26 and the shell 11. Theprimary separation takes place on their edges so that the sleeves willintercept the spinning carrier fluid in its axial movement, with thetherein suspended solid particles. Said edges define the primaryseparation area; they are preferably beveled, and the thereby separatedfluid carrier with therein suspended material will continue to spin insaid annular spaces after having been separated by said edges. Thedownwardly spinning mixture within the annular spaces 25', 26' and 31,being subject to a further density stratification, is separated in thesecondary separation areas which are defined by the edges of shortersleeves 27, 28 and 30, placed inside the annular spaces 25', 26 and 31.A tertiary separation area is provided in the annular space 26, by theis formed by the sleeve 30 and the shell 11. In the bottom 13, eachannular space is provided with an outlet, draining the respectiveseparation area; these outlets are marked by numerals 32 to 39respectively. All of the annular spaces, except numeral 24', are furtherprovided with drain regulating covers 40, fixed at a small distance fromthe bottom 13. A cover 40 is shown in plan view in Figure 2, between theshell 11 and the sleeve 30. It is a large washer of a thin material assheet metal, provided with a series of openings 41, varying fromrelatively small to large in cross-sectional area. The smallest Opening41 is close to the outlet 39, the largest opening 41 is most remote fromthe outlet 39. The volume of flow passing through the largest opening 41must travel the longest distance to reach the outlet 39. The shorter thedistance for the fluid to reach the outlet 39, the smaller the opening41, so that the fluid passing through any one of the openings 41 has toovercome the same resistance. Therefore, equal volumes of fluid willpass through each opening 41, whatever its size. In this manner, thespinning fluid will *3 be drained evenlyalong the whole circumference ofeach annular space, thus avoiding any turbulence in the adjacentseparating areas. The outlet 32 in the circular space '24'"is locatedcentrally in said space,andwill drain evenly saidspacewithout any cover.The volume offluid"passing through the outlets mustbecontrollable 'inor'derto "obtain maximum'efiiciency of separation in the annular spaces.Many conventional control devices may-'be used for this purpose. Figure4 shows one possible'solution for controlling the primary andsecondaryseparations in the annular-spaces 24,"27"and28', containing theclean carrier and fine solid components of 'theseparated material. The utlet'32'evacuates the clean carrier fluid obtained from the primaryseparation in the space 24'. Numeral -32',which mayor may notexist, isan auxiliary outlet for illustration purposes only. 'Baflies6ll,-65,66-and 66' "are pivotally mounted in the 'walls of the "outlets 32, 32',33 and 34, by journals 62, the lever arms 63 forming one piece-withthebafiles 'and with the journals, will move "saidbaffles. The control ofthe flow through the outlets 33' and 34 is' regulated by a triangularguide'64. Oneside of-this guide-64actuates, through the lever arm 63,making sliding contact therewith-as'a follower, the baffle61 in the"outlet' 34, the other side of the same guide actuates the baflie 65 inthe outlet 33. A similar triangular guide 64 *'makes sliding contactwith the baffles 66 and 66' in the outlets 32 and 32'. 'The triangularguides 64 are coupled by a bar 67, which is supported in its center by afulcrum 68. This fulcrum maybe moved horizontally a short distance; italso allows a slightpivoting movement of the two'guides 64, so that avertical movement of one of them in'one direction causes the other guideto move in the op- 'posite direction. When the fulcrum 68 is movedhorizontally to the right, the volumeof flow drained by the out-'-lets'32 and 32', if any, will be decreased to the same ex- "tent. Thesame movement to the left will reverse the ef- -"fect in the sameoutlets. An upward movement'ofthe guide 64 on the left hand side, Willincrease'the volume drained by the two outlets 33 and 34, to the sameextent in eachmember of thiscouple, while simultaneously the 'guideonthe right hand side will cause a'reduction of the volume drained by theoutlets 32 and 32,al'so to-the same-extent in each member of the couple.Asit can be seen in' Figure 1,by this way of control, the total voli umeof carrier fluid handled by the spaces 24=and 25 can bemaintainedconstant, even though the ratio'of volumes handled by each of the twospaces can be changed, so that Jthe other parts of the sameprimaryseparation area will not be influenced by this change. Similarly,the ratiozof "volumes of fluid yielded by the two secondary separation:areas in thespace 25', outlet 34, and the'space 27, outlet I 33, can bechanged without changing anything in the re- Lspecttve primaryseparation area.

In operation, consider a concentrated mixture of copper-nickel-iron orewith rock particles, suspended in wa- "ter, to be separated. The densityof the nickel ore being -4.8, that of iron ore 4.6, copper ore 4.2, rock28, and water 1.0. The particles in the mixture have been previouslycomminuted and screened approximately to equal -grainsize. A cleancarrier fluid, such as pure water, is :fed tangentially into the vortexchamber 23 through the inlet pipe'21 and the inlet 22, and is spinningin the cham- "ber 23. This helical spin has a slight radially inwardldi-Irection, as shown by arrows, because the major part of this carrier isdrained by the outlets 32, 33 and 34. The separable mixture is fedthrough the pipe past the :spin imparting vanes and the nozzle 19 intothe chamber-23. The 'sepa'rable'material i spinning radially outwardly,thus forming in the spinning carrier a truncated cones'sb's,shownbyidotted lines in Figure 1. The nickel ore particles having thegreatest density, will spread faster in the direction of the radius thanthe other components:' due to higher inertia, they will work their way=through'the spinning carrier under the impulse of the centrifugaltension faster and easier, thus, they will spread thelongest distanceradially outward, before they are intercepted. The rock particles havingthe smallest momentum, will remain in the central portion of thespinning water, since their radial escape is slower and, moreover, theyare unable to overcome the resistance of the carrier spinning toward thecentralzsleeve partitions 24 and 25. Out of two particles of the samesize, but unequal density, spread simultaneously .by'the nozzle '19, theheavier one will travel a greater distance in the direction of theradius in-a unit of time. 'The iron'and copperparticles will be spinningat intermediate distances, their velocity in the radial direction beingproportional to their respective densities. The position of the nozzle19is vertically adjusted in such a way that thenickeliparticles will beintercepted by the annular space 31, between the edge of the sleeve 26and the shell 11. The iron ore particles will be intercepted by theannular space 26', the copper particles by the space 25,and the muchlighter rock by the space'24'.

'Furthersub-separations take place within the annular spaces 31, 26' and25', as the intercepted fiuid continues to spin downwardly and tofurther stratify itself in density layers. Due to this furtherStratification, nickel ore particles-will be collected by theannularspace 31' and evacuatedwith a minimumof carrier fluidby the outlet 39,

while most of carrier fluid intercepted by the space '31 'will passthrough the annular space 30' and the outlet 38,

provided, this outlet 38 is more open than the outlet 39.

Thus, the'nickel ore has been thickened by asecondary separation withinthe space 31. Similarly, the copper'ore particles intercepted "by thespace 25 will be thickened in the secondary separation area defined bythe edge of the partition sleeve 27 and by the adjacent sleeves 24 and25;

the outlet 33 being open,will evacuate'most of the carrier fluidintercepted-by the space 25',while the outlet 34, 35'

copper ore particles with a minimum 'of'carrier fluid.

with'a passage reduced by the baffle, will'evacuate all The iron' oreparticles intercepted" by the annular space 26' are thickened inasecondary separation by the edge'of the partition sleeve 28 andlosemost of the carrier, which will travel'through the -secondary-space28' and the outlet 35, while the iron ore particles with a remainder ofthe carrier 'willenter the tertiary separation area defined by theedgeofthe partitionsleeve 29. This reduced flow rotates now at a lowspeed,the centrifugal tension is less active; and a lighter part'of thesuspended iron ore, repre- "sentingamiddling, maybe thus intercepted bythe annular-space'29', to -be-evacuated bythe outlet 36, While theheavier'part of the same iron ore is drained by theoutlet 37. 'The ratioof partial flows in the tertiary separation depends on the position ofthebafiles in the respective out- -letscontr0lling said'partial flows;the separation'may be assisted by making the annular space 26 narrowerin the "zone of the tertiary separation area. The lighter rockparticles, unable to 'escape'radially outwardly, will beintercepted-With most of the carrier fluid by the space 24" and"evacuated by the outlet 32. It is obvious that the rock particles may'besubjected-to a secondary separation as 'the othercomponents,ifdesired, and that any number of 'sleeves' may be employed in thisapparatus, depending on the mixture to-be separated. Particles ofintermediate densities formed of rock and ore, or of two or three kindsof ore, may be intercepted as middlings and thickened as such, in a moredeveloped system of intercepting sleeves.

i Ifa radiallyinward fluid flow is desired, the central outlet'pa'ssages 32 and 33 rreceive the largest part of the carrier fluid,thereby promoting'the desired lateral pressure of the A suf- 'in avortex "chamber of a certainvertical height,-wherein the distance of thetangential inlet 22 from the interceptingQsleeves-24, 25 and-26 islarge, the-helical fluid flow will tend to rotate rather in the centerof space 23, cutting short its way towards the outlets 32,33 and 34,while the remote peripheral layers will be idle, thus, little or nolateral pressure. This condition may be corrected by installing inthechamber 23, one or more feeding sleeves 42, marked in dotted lines. Thespinning carrier directed by the lower edges of the sleeves 42 willexert a lateral pressure at any desired height in the conicallyoutstretched fine solid material; the sleeves should be suspended fromthe wall 11 by brackets shaped as helical vanes, to prevent anyturbulence in the spinning carrier.

-In density separations requiring high accuracy, as in the above quotedexample of components differing very little in their respectivedensities, such a lateral pressure may be very useful, especially whenit can be made variable in any convenient manner, to subject the treatedmixture to a severe density test. This can be achieved by feeding anadditional carrier fluid flow into the vortex chamber 23 radiallyinwardly, discharging a flow into the primary separation area itselffrom outside. In the Figure 3, a modification of the shell 11 fromFigure 1 is shown, meeting said requirements, the details of thesecondary and tertiary separations are omitted. The general outline ofthe primary separation area defined by edges of the partition sleeves 52to 55 is here concave, an auxiliary vortex chamber is provided on theoutside periphery of the housing. The housing of the apparatus consistsof two parts 43 and 44; they both are flanged so that the lower part 44provides a shell 46 defining the outward periphery of an auxiliaryvortex chamber 47, while the upper part 43 provides a cover 45 for thesame, the two parts 43 and 44 being connected by flanged edges 48 on thewhole circumference. This outer connection is tight and will be securedby a gasket of a suitable thickness, not shown in the drawing. When thetwo parts 43 and 44 are assembled as shown, there is formed a slot 49 ofa uniform width along the whole circumference of the chamber 23,connecting the main vortex chamber 23 with the auxiliary chamber 47.Obviously, the width of the slot 49 may be changed by inserting a gasketof a suitable thickness at 48. The additional fluid is fed in by thetube 50 and the tangential inlet 51 into the chamber 47; this flow iscontrollable by a baffle. The lateral pressure produced by this devicein the direction of the arrows is most eflicacious in precision work,such as described above. It can be seen from the Figure 3 that the wholeseparating process is performed in the central parts of the spinningcarrier, that a contact between the structure parts and the separablematerial is reduced to a minimum, thus avoiding the well known corrosionby friction of fine solids on the apparatus walls. The separablematerial stretches out from the feed pipe in the form of a cone sb-s andwill be completely intercepted by the partition sleeves. The lateralpressure of the flow coming from the slot 49 and acting upon the slantside of the cone sbs, must be set up by the control in the tube 50, soas to deflect particles of lower selected density towards the centralintercepting sleeves, while the heavier ones overcome said lateralpressure and are intercepted by the outer sleeves.

The viscosity of the carrier fluid is a constant obstacle to a lateralpenetration, and is that factor which makes, in this method, densityseparations possible. In precision work as cited above, it is necessarythat all particles leaving the nozzle 19, start their spinning motion atthe very moment of discharge, if they are to be correctly separated.This requirement is not always met in a single discharge nozzle 19, asshown in Figure 1, wherein the flow leaving said nozzle forms a solidcylinder containing the axis of the spin. There is little or no radiusof rotation in this cylinder axis, thus, there is little or nocentrifugal tension to move the particles radially into the spinningfluid. As said cylinder disintegrates progressively in the adjacentspinning carrier, a small cone of the handled material projectsdownwardly from the discharge nozzle 19, and will be spread later thanthe In Figure 5, a new feed pipe 70 is shown, which cor rects thiscondition. The pipe 70 is provided with a core, concentric pipe 71, andthe annular space between them has spin imparting vanes 72, of anyconventional type. The pipe 71 has its own helix 73. A fine solidmaterial discharged by this device, will leave by said annular space,and all its particles will start rotating instantly as soon asdischarged. The effect may be further assisted by feeding a cleancarrier fluid through the core pipe 74. The spreading solids s will forma thin layer, achieving a perfect density spectrum at the base b,provided, the discharged particles have a fairly uniform size. Out oftwo particles of the same density, the larger one will penetratelaterally faster than the smaller one; this must be considered, whereverfine density differences are to be achieved by this new method. In theseparation of materials in which the respective densities of thecomponents are far apart from each other, relatively large grain sizedifferences are admissible. For instance, in threshing operations, thefiner part of the output of a thresher discharged by a single feed pipe15 into a spinning air column, is separated correctly, even though thekernels diifer sharply in size from the accompanying dust and strawparticles.

It will be noted that the abrasive effect of the handled material on theseparating members may be avoided by providing them with a rubbercoating or alike. The friction in the intercepting sleeves is reduced bygiving them a conical shape as shown in Figures 1 and 3, which providesa reduced friction angle. At the same time, the bottom space, needed forconnections is larger and helpful for slowing down the angular velocityof the partial flows before their evacuation. The use of draining covers40 with openings 41 can be avoided, either by enlarging said bottomspace downwardly so that the distance of an outlet from the respectiveseparation area is large enough to stop the spin, or by increasing thenumber of outlets in each bottom space, to drain the whole circumferencethereof evenly, or by combination of both methods. Obviously, the bottom13 may be flat as well, or project into the vortex chamber 23.Connections of structure parts by seam or spot welding have beencontemplated in the drawings shown. Wherever covers 40 are used, theopenings 41 along the centerline of a cover may be substituted for byperipheral indentures of a varied size.

In the description of the method steps and structure parts given above,many variations may be made without departing from the scope of thisinvention. Therefore, the details disclosed are not limitative of theembodiments of the invention except as claimed hereinafter:

I claim:

An apparatus for multiple separation of suspended fine solids by densitydifference, comprising in combination: a closed main vortex chamberhaving a substantially horizontal top portion, a circular wall section,and a bottom portion, a circumferential gap in said wall section, anauxiliary vortex chamber arranged concentrically outwardly of said mainvortex chamber in a radially adjacent position thereto, said gapconnecting said auxiliary chamber to said main vortex chamber, feedingmeans in said circular wall section adapted to feed and to rotate acarrier fluid in said main vortex chamber, feeding means in saidauxiliary vortex chamber adapted to feed and to rotate therein anadditional carrier fluid, separate feeding means for a mixture of finesolid particles arranged concentrically with said main vortex chamberand substantially perpendicular to said feeding means and movable in anaxial direction thereto, said separate feedthe same time from the same 7ing means having a mouth open in an, axial direction and being able todischarge said mixture axially so as to spread it radially outwardly ina fine layer into said spinning carrier, a first series of partitionsleeves arranged concentrically Within said main vortex chamber andproviding primary annular spaces to split into fractions said carrierfluid with said particles suspended therein, a second series ofpartition sleeves arranged concentrically within said primary annularspaces and providing secondary annularv spaces, a partition sleeve oftertiary separation within one of said secondary annular spaces, anddraining means for each of said annular spaces.

References Cited in the file of this patent UNITED STATES PATENTS Frazerj Sept. 11-, 1955 Fontein Nov. 6; 1 9562 Chisholm Mar. 5, 1957 RakowskyJuly-15, 1 9-58:

FOREIGN PATENTS Germany Jan. 12, 195

Italy Jan. 22, i954

